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We use the Sloan Digital Sky Survey Data Release 12, which is the largestavailable white dwarf catalog to date, to study the evolution of thekinematical properties of the population of white dwarfs in the Galactic disc.We derive masses, ages, photometric distances and radial velocities for allwhite dwarfs with hydrogen-rich atmospheres. For those stars for which propermotions from the USNO-B1 catalog are available the true three-dimensionalcomponents of the stellar space velocity are obtained. This subset of theoriginal sample comprises 20,247 objects, making it the largest sample of whitedwarfs with measured three-dimensional velocities. Furthermore, the volumeprobed by our sample is large, allowing us to obtain relevant kinematicalinformation. In particular, our sample extends from a Galactocentric radialdistance $R_{\rm G}=7.8$~kpc to 9.3~kpc, and vertical distances from theGalactic plane ranging from $Z=-0.5$~kpc to 0.5~kpc. We examine the meancomponents of the stellar three-dimensional velocities, as well as theirdispersions with respect to the Galactocentric and vertical distances. Weconfirm the existence of a mean Galactocentric radial velocity gradient,$\partial\langle V_{\rm R}\rangle/\partial R_{\rmG}=-3\pm5$~km~s$^{-1}$~kpc$^{-1}$. We also confirm North-South differences in$\langle V_{\rm z}\rangle$. Specifically, we find that white dwarfs with $Z>0$(in the North Galactic hemisphere) have $\langle V_{\rm z}\rangle<0$, while thereverse is true for white dwarfs with $Z<0$. The age-velocity dispersionrelation derived from the present sample indicates that the Galactic populationof white dwarfs may have experienced an additional source of heating, whichadds to the secular evolution of the Galactic disc.

The kinematics of the white dwarf population from the SDSS DR12